[ovs-dev] [dpdk-howl PATCH v5 2/2] netdev-dpdk: Set scatter based on capabilities

Ophir Munk ophirmu at mellanox.com
Sat Oct 13 21:12:12 UTC 2018


On , October 12, 2018 12:25 PM Eelco Chaudron wrote:

> 
> On 10 Oct 2018, at 18:14, Ophir Munk wrote:
> 
> > Before this commit setting scatter offload was based on checking
> > net_nfp device.
> > Since DPDK 17.11 more PMD drivers are reporting offload capabilities.
> > Therefore this commit removes the specific check against net_nfp
> > device and replaces it with a generic check of device capabilities
> > before setting the scatter offload.
> >
> > Signed-off-by: Ophir Munk <ophirmu at mellanox.com>
> > ---
> >
> > v1-v4
> > This patch was not included in version v1-v4 of the series
> >
> > v5
> > Initial version
> >
> >  lib/netdev-dpdk.c | 18 ++++++++++++------
> >  1 file changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c index
> > 4dd0ec3..ecca276 100644
> > --- a/lib/netdev-dpdk.c
> > +++ b/lib/netdev-dpdk.c
> > @@ -367,6 +367,7 @@ struct ingress_policer {  enum
> dpdk_hw_ol_features
> > {
> >      NETDEV_RX_CHECKSUM_OFFLOAD = 1 << 0,
> >      NETDEV_RX_HW_CRC_STRIP = 1 << 1,
> > +    NETDEV_RX_HW_SCATTER = 1 << 2
> >  };
> >
> >  /*
> > @@ -894,13 +895,11 @@ dpdk_eth_dev_port_config(struct netdev_dpdk
> > *dev, int n_rxq, int n_txq)
> >      rte_eth_dev_info_get(dev->port_id, &info);
> >
> >      /* As of DPDK 17.11.1 a few PMDs require to explicitly enable
> > -     * scatter to support jumbo RX. Checking the offload capabilities
> > -     * is not an option as PMDs are not required yet to report
> > -     * them. The only reliable info is the driver name and knowledge
> > -     * (testing or code review). Listing all such PMDs feels harder
> > -     * than highlighting the one known not to need scatter */
> > +     * scatter to support jumbo RX.
> > +     * Setting scatter for the device is done after checking for
> > +     * scatter support in the device capabilites. */
> >      if (dev->mtu > ETHER_MTU) {
> > -        if (strncmp(info.driver_name, "net_nfp", 7)) {
> > +        if (dev->hw_ol_features & NETDEV_RX_HW_SCATTER) {
> >              conf.rxmode.offloads |= DEV_RX_OFFLOAD_SCATTER;
> >          }
> >      }
> > @@ -1035,6 +1034,13 @@ dpdk_eth_dev_init(struct netdev_dpdk *dev)
> >          dev->hw_ol_features |= NETDEV_RX_CHECKSUM_OFFLOAD;
> >      }
> >
> > +    if (info.rx_offload_capa & DEV_RX_OFFLOAD_SCATTER) {
> > +        dev->hw_ol_features |= NETDEV_RX_HW_SCATTER;
> > +    } else {
> > +        /* Do not warn on lack of scatter support */
> > +        dev->hw_ol_features &= ~NETDEV_RX_HW_SCATTER;
> 
> Don’t think we need to clear it explicitly, none of the other capabilities do
> this.

The other capabilities do clear explicitly.
There is a difference between NETDEV_RX_HW_SCATTER flag (which should be set or cleared in dpdk_eth_dev_init()) and DEV_RX_OFFLOAD_SCATTER flag (which is only set in dpdk_eth_dev_port_config()). 

Flags of type "NETDEV_RX_XXXXXX" are cleared explicitly. For example, we clear:
dev->hw_ol_features &= ~NETDEV_RX_HW_CRC_STRIP;
dev->hw_ol_features &= ~NETDEV_RX_CHECKSUM_OFFLOAD;

in the following code snippet:
    if (strstr(info.driver_name, "vf") != NULL) {
        VLOG_INFO("Virtual function detected, HW_CRC_STRIP will be enabled");
        dev->hw_ol_features |= NETDEV_RX_HW_CRC_STRIP;
    } else {
        dev->hw_ol_features &= ~NETDEV_RX_HW_CRC_STRIP;
    }

    if ((info.rx_offload_capa & rx_chksm_offload_capa) !=
            rx_chksm_offload_capa) {
        VLOG_WARN("Rx checksum offload is not supported on port "
                  DPDK_PORT_ID_FMT, dev->port_id);
        dev->hw_ol_features &= ~NETDEV_RX_CHECKSUM_OFFLOAD;
    } else {
        dev->hw_ol_features |= NETDEV_RX_CHECKSUM_OFFLOAD;
    }

    if (info.rx_offload_capa & DEV_RX_OFFLOAD_SCATTER) {
        dev->hw_ol_features |= NETDEV_RX_HW_SCATTER;
    } else {
        /* Do not warn on lack of scatter support */
        dev->hw_ol_features &= ~NETDEV_RX_HW_SCATTER;
    }

During configuration we only set DEV_RX_OFFLOAD_SCATTER flag:
    if (dev->mtu > ETHER_MTU) {
        if (dev->hw_ol_features & NETDEV_RX_HW_SCATTER) {
            conf.rxmode.offloads |= DEV_RX_OFFLOAD_SCATTER;

I suggest keeping the patch as is.

> For the rest this patch look good to me.
> 
> > +    }
> > +
> >      n_rxq = MIN(info.max_rx_queues, dev->up.n_rxq);
> >      n_txq = MIN(info.max_tx_queues, dev->up.n_txq);
> >
> > --
> > 1.8.3.1
> >
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